Water filter incorporating activated carbon particles with surface-grown carbon nanofilaments

ABSTRACT

A filter for producing potable water filter comprises a housing including a water inlet and a water outlet, and a filter material arranged within the housing. The filter material comprises activated carbon particles, and a plurality of carbon nanofilaments disposed on the surface of the activated carbon particles. The filter is operable to provide potable water by removing contaminants from a liquid water stream flowing from the water inlet to the water outlet of the housing.

FIELD OF THE INVENTION

The present invention relates to water filters, and specifically relatesto water filters employing filter material comprising activated carbonparticles and carbon nanofilaments on the particle surface, and methodsof making and using the same. More specifically, the water filters aredirected to removing contaminants from a water stream to provide potablewater.

BACKGROUND OF THE INVENTION

Water may contain many different kinds of contaminants including, forexample, particulates, harmful chemicals, and microbiological organisms,such as bacteria, parasites, protozoa and viruses. In a variety ofcircumstances, these contaminants must be removed before the water canbe used. For example, in many medical applications and in themanufacture of certain electronic components, extremely pure water isrequired. As a more common example, any harmful contaminants must beremoved from the water before it is potable, i.e., fit to consume.Despite modern water purification means, the general population is atrisk, and in particular infants and persons with compromised immunesystems are at considerable risk.

In the U.S. and other developed countries, municipally treated watertypically includes one or more of the following impurities to variouslevels: suspended solids, chemical contaminants, such as organic matter,and heavy metals, and microbiological contaminants, such as bacteria,parasites, and viruses. Breakdown and other problems with watertreatment systems sometimes lead to incomplete removal of thesecontaminants. In other countries, there are deadly consequencesassociated with exposure to contaminated water, as some of them haveincreasing population densities, increasingly scarce water resources,and no water treatment utilities. It is common for sources of drinkingwater to be in close proximity to human and animal waste, such thatmicrobiological contamination is a major health concern. As a result ofwaterborne microbiological contamination, an estimated six millionpeople die each year, half of which are children under 5 years of age.

The reduction of the general contaminant concentration in the potablewater takes place at the municipal treatment facilities and in homeswith point-of-entry (POE) and/or point-of-use (POU) water filters. Thisreduction in concentration in the home water filters is achieved bymechanical filtration, (i.e., size exclusion for some particulates,parasites, and bacteria), and adsorption (i.e., chemicals, someparticulates, parasites, bacteria, and viruses). For home water filters,the concentration reduction levels depend on the flowrate, filter volumeand shape, influent concentration levels, and capture kinetics andcapacity of the filtration medium. For the purposes of this invention,the capture kinetics and capacity of the medium is encompassed in theterm “capture efficiency”. Furthermore, if the concentration reductionlevels achieved by home water filters reach the levels mandated byvarious domestic or international organizations (e.g., U.S.Environmental Protection Agency—EPA, National Sanitation Foundation—NSF,and World Health Organization—WHO) in pertinent testing standards andprotocols, then the water filters can be registered by theseorganizations and carry the applicable registration numbers. Similartests and standards apply to air filters.

For example, the EPA introduced the “Guide Standard and Protocol forTesting Microbiological Water Purifiers” in 1987. This protocolestablishes minimum requirements regarding the performance of drinkingwater treatment systems that are designed to reduce specific healthrelated contaminants in public or private water supplies. Therequirements are that the effluent from a water supply source exhibits99.99% (or equivalently, 4 log) removal of viruses and 99.9999% (orequivalently, 6 log) removal of bacteria against a challenge. Under theEPA protocol, in the case of viruses, the influent concentration shouldbe 1×10⁷ viruses per liter, and in the case of bacteria, the influentconcentration should be 1×10⁸ bacteria per liter. Because of theprevalence of Escherichia coli (E. coli, bacterium) in water supplies,and the risks associated with its consumption, this microorganism isused as the bacterium in the majority of studies. Similarly, the MS-2bacteriophage (or simply, MS-2 phage) is typically used as therepresentative microorganism for virus removal because its size andshape (i.e., about 26 nm and icosahedral) are similar to many viruses.Thus, a filter's ability to remove MS-2 bacteriophage demonstrates itsability to remove other viruses.

Similar protocols and/or standards exist for chemical and particulateconcentration reductions established by NSF. For example, NSF/ANSIStandard 42 covers the aesthetic effects of POU and POE systems designedto reduce specific aesthetic or non-health-related contaminants, such aschlorine, taste and odor, and particulates. Similarly, NSF/ANSI Standard53 covers the health effects of POU and POE systems designed to reducespecific health-related contaminants, such as Cryptosporidium, Giardia,lead, volatile organic chemicals (VOCs), and methyl tertiary-butyl ether(MTBE).

Due to these requirements and a general interest in improving thequality of potable water, there is a continuing desire to provideimproved filters and filter materials capable of removing contaminantsfrom a water stream, as well as a desire to provide improved methods ofmaking and using the filter materials, and filters incorporating thefilter materials.

SUMMARY OF THE INVENTION

According to a first embodiment, a filter for producing potable water isprovided. The filter comprises a housing including a water inlet and awater outlet, and a filter material arranged within the housing. Thefilter material comprises activated carbon particles, and a plurality ofcarbon nanofilaments disposed on the surface of the activated carbonparticles. The filter is operable to provide potable water by removingcontaminants from a liquid water stream flowing from the water inlet tothe water outlet of the housing.

According to a second embodiment, a method for producing potable wateris provided. The method comprises providing a filter comprising ahousing including a water inlet and a water outlet, and a filtermaterial arranged within the housing. The filter material comprises aplurality of carbon nanofilaments disposed on the surface of theactivated carbon particles. The method further comprises passing a waterstream through the filter material to remove contaminants and therebyproduce potable water.

According to a third embodiment, a method of making a filter materialfor producing potable water is provided. The method comprises providingactivated carbon particles, depositing one or more nanofilamentprecursors at least partially onto the surface of the activated carbonparticles, agitating the activated carbon particles and the depositednanofilament precursors in the presence of carbonaceous vapor, andheating the activated carbon particles and the deposited nanofilamentprecursors in the presence of carbonaceous vapor at a temperature andtime sufficient to produce the filter material comprising activatedcarbon particles having carbon nanofilaments on the surface of theparticles.

According to a fourth embodiment, a method of making a filter materialfor producing potable water is provided. The method comprises providingcarbonized carbon particles, depositing one or more nanofilamentprecursors at least partially onto the surface of the carbonized carbonparticles, agitating the carbonized carbon particles and the depositednanofilament precursors in the presence of carbonaceous vapor, heatingthe carbonized carbon particles and the deposited nanofilamentprecursors in the presence of carbonaceous vapor at a temperature andtime sufficient to produce carbon nanofilaments on the surface of thecarbonized carbon particles, and activating the carbonized carbonparticles by heating or chemically treating the carbonized particles andcarbon nanofilaments to produce the filter material comprising activatedcarbon particles having carbon nanofilaments on the surface of theparticles.

Filters for producing potable water, and the methods of making and usingthe filter material incorporated in the filter according to theinvention are advantageous in the removal of contaminants from a waterstream. Additional features and advantages provided by the filters,filter materials, and methods of the present invention will be morefully understood in view of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the invention, it is believed that the presentinvention will be better understood from the following description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a Scanning Electron Microscope (SEM) image of a prior artactivated carbon particle;

FIG. 2 a is an SEM image of an activated carbon particle according toone or more embodiments of the present invention;

FIG. 2 b is another SEM image of an activated carbon particle accordingto one or more embodiments of the present invention;

FIG. 2 c is a higher magnification SEM image of an activated carbonparticle according to one or more embodiments of the present invention;and

FIG. 3 is a cross sectional side view of a filter according to one ormore embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION I. Definitions

As used herein, the terms “filters” and “filtration” refer to structuresand mechanisms, respectively, associated with reduction of concentrationof contaminants, i.e., particulates, chemical and microbiologicalcontaminants, via either adsorption and/or size exclusion.

As used herein, the phrase “filter material” is intended to refer to anaggregate or collection of filter particles. The aggregate or collectionof the filter particles forming a filter material can be eitherhomogeneous or heterogeneous, and can take any shape or form. The filterparticles can be uniformly or non-uniformly distributed (e.g., layers ofdifferent filter particles) within the filter material. The filterparticles forming a filter material also need not be identical in shapeor size and may be provided in either a loose or interconnected form.For example, a filter material might comprise activated carbon particleswith surface-grown nanofilaments in combination with activated carbonfibers or mesoporous and basic activated carbon particles, and thesefilter particles may be either provided in loose association orpartially or wholly bonded by a polymeric binder or other means to forman integral structure.

As used herein, the phrase “filter particle” is intended to refer to anindividual member or piece, which is used to form at least part of afilter material. For example, a fiber, a granule, a bead, etc. are eachconsidered filter particles herein. Further, the filter particles canvary in size, from impalpable filter particles (e.g., a very finepowder) to palpable filter particles.

As used herein, the term “nanofilament” and its derivatives refer tocarbon hollow or solid structures with lateral dimension (e.g.,diameter, width, or thickness) on the order of nanometers (nm) andlongitudinal dimension (e.g., length) from a few nanometers to hundredsof microns (μm), which emanate and protrude from the surfaces of theactivated carbon particles. A non-limiting list of examples ofnanofilaments of the present invention includes single-wall nanotubes(SWNTs), double-wall nanotubes (DWNTs), multi-wall nanotubes (MWNTs),nanofibers, nanoribbons, nanohorns, or mixtures thereof.

As used herein, the term “contaminant” and its derivatives may refer toany of the following 3 categories: particulates (e.g., turbidity, andinsoluble inorganic particles such as calcium carbonate), chemicals(e.g., chlorine, taste, odor, VOCs, asbestos, atrazine, MTBE, arsenicand lead), microbiological organisms (e.g., bacteria, viruses, algae,and parasites), or combinations thereof. Further contaminants are alsocontemplated herein.

As used herein, the term “carbonization” and its derivatives areintended to refer to a process in which the non-carbon species in acarbonaceous substance are reduced.

As used herein, the term “activation” and its derivatives are intendedto refer to a process in which a carbonized substance is rendered moreporous.

As used herein, the term “activated particles” and its derivatives areintended to refer particles that have been subjected to an activationprocess.

As used herein, the term “deposition” and its derivatives refer toprocesses that deliver particles or generally substances onto or into asubstrate. Non-limiting examples of deposition processes are adsorptionand mixing. Additional deposition examples included electrochemicaldeposition, electron-beam evaporation, thermal vapor deposition, and/orradio frequency magnetron sputtering.

II. Embodiments

In accordance with one embodiment as shown in FIG. 3, a filter 20 forproducing potable water is provided. The filter 20 comprises a housing22 including a water inlet 24 and a water outlet 26. The FIG. 3embodiment illustrates a cylindrical shaped embodiment; however, thehousing 22 can be provided in a variety of forms, shapes, sizes, andarrangements depending upon the intended use of the filter, as known inthe art. For example, the filter can be an axial flow filter, whereinthe inlet and outlet are disposed so that the liquid flows along theaxis of the housing. Alternatively, the filter can be a radial flowfilter wherein the inlet and outlet are arranged so that the fluid flowsalong a radial of the housing. Still further, the filter can includeboth axial and radial flows. The housing may also be formed as part ofanother structure without departing from the scope of the presentinvention.

The size, shape, spacing, alignment, and positioning of the inlet 24 andoutlet 26 can be selected, as known in the art, to accommodate the flowrate and intended use of the filter 20. Preferably, the filter 20 isconfigured for use in residential or commercial potable waterapplications. Examples of filter configurations, potable water devices,consumer appliances, and other water filtration devices suitable for usewith the present invention are disclosed in U.S. Pat. Nos. 5,527,451;5,536,394; 5,709,794; 5,882,507; 6,103,114; 4,969,996; 5,431,813;6,214,224; 5,957,034; 6,145,670; 6,120,685; and 6,241,899, thesubstances of which are incorporated herein by reference. According tomultiple potable water embodiments, the filter 20 may be configured toaccommodate a flow rate of less than about 8 L/min of water, or lessthan about 6 L/min, or from about 2 L/min to about 4 L/min

Referring to FIG. 3, the filter 20 comprises filter material 28 arrangedin the housing 22. The housing 22 may contain as much filter material 28as desired by the filtering application. The housing may contain lessthan about 2 kg of filter material, or less than 1 kg of filtermaterial, or less than 0.5 kg of filter material. The filter particlespresent in the filter material 28 are activated carbon particles havinga plurality of carbon nanofilaments disposed on the surface of theactivated carbon particles. The filter particles may comprise a varietyof shapes and sizes. For example, the filter particles can be providedin simple forms such as granules, fibers, and beads. The filterparticles can be provided in the shape of a sphere, polyhedron,cylinder, as well as other symmetrical, asymmetrical, and irregularshapes. Further, the filter particles can also be formed into complexforms such as webs, screens, meshes, non-wovens, wovens, and bondedblocks, which may or may not be formed from the simple forms describedabove.

Like shape, the size of the filter particles can also vary, and the sizeneed not be uniform among filter particles used in any single filter. Infact, it can be desirable to provide filter particles having differentsizes in a single filter. The filter particles may have a size of about0.1 μm to about 10 mm. In exemplary embodiments, the filter particlesmay have a size of about 0.2 μm to about 5 mm, from about 0.4 μm toabout 1 mm, or from about 1 μm to about 500 μm. For spherical andcylindrical particles (e.g., fibers, beads, etc.), the above-describeddimensions refer to the diameter of the filter particles. For filterparticles having substantially different shapes, the above-describeddimensions refer to the largest dimension (e.g., length, width, orheight).

The filter particles may comprise any suitable activated carbonparticles, or in some embodiments, pre-activated carbonized carbonparticles. For example and not by way of limitation, the activatedcarbon particles can be microporous, mesoporous, or combinationsthereof. Furthermore, the activated carbon particles may comprisewood-based activated carbon particles, coal-based activated carbonparticles, peat-based activated carbon particles, pitch-based activatedcarbon particles, tar-based activated carbon particles, or combinationsthereof. The filter material 28 may be provided in either a loose orinterconnected form (e.g., partially or wholly bonded by a polymericbinder or other means to form an integral structure).

Activated carbon particles with surface-grown nanofilaments have captureefficiencies for contaminants higher than activated carbon particleswithout nanofilaments. A scanning electron micrograph (SEM) of anactivated carbon particle without nanofilaments is shown in FIG. 1, andSEM's of activated carbon particles with surface-grown nanofilaments areshown in FIGS. 2 a and 2 b. In one of many contemplated filteringembodiments, a large number of surface-grown nanofilaments may yieldmore adsorption sites and a large number of size exclusion sites for thevarious contaminants. During operation of the filter 20, a water streampasses from the water inlet 24 to the water outlet 26 of the filter 20.As the water stream passes though the filter material 28, contaminantsare removed in order to deliver potable water through the water outlet26 of the filter 20. In one embodiment, this contaminant removal mayresult from contaminant adsorption to the adsorption sites of the filterparticles.

In accordance with another embodiment, a method of making filtermaterial 28 for producing potable water is provided. The methodcomprises providing activated carbon particles, and depositing one ormore nanofilament precursors at least partially onto the surface of theactivated carbon particles. The nanofilaments may be deposited via anysuitable conventional technique known to one skilled in the art.Examples of deposition techniques are provided in the definition sectionabove. In one embodiment, these nanofilament precursors comprisecatalysts and may be present in a solid, liquid or gas phase. In aspecific embodiment, the nanofilament precursors comprise catalysts,which comprise salts of transition metals. These salts of transitionmetals may include Fe, Co, Mo, and Ni, or mixtures thereof. Examples ofthe nanofilament precursors, include, but are not limited to, ferricsulfate ((Fe₂(SO₄)₃), ferric chloride (FeCl₃), ferrocene (Fe(C₅H₅)₂),cobaltocene (Co(C₅H₅)₂), nickelocene (Ni(C₅H₅)₂), ferric oxide (Fe₂O₃),iron pentacarbonyl (Fe(CO)₅), and nickel phthalocyanine (C₃₂H₁₆N₈Ni).

The method further comprises agitating the activated carbon particlesand deposited nanofilament precursors in the presence of carbonaceousvapor, and heating the activated carbon particles and the depositednanofilament precursors in the presence of carbonaceous vapor at atemperature and time sufficient to produce the filter materialcomprising activated carbon particles having carbon nanofilaments on thesurface of the particles. In accordance with the method, thecarbonaceous vapor contacts and reacts with the activated carbonparticles and deposited nanofilament precursors in a heated environment,for example, a furnace or reactor. If the activated carbon particles anddeposited nanofilaments are arranged in a stationary configuration e.g.inside a fixed-bed flow reactor, the carbonaceous vapor will likelycontact only the top layer of the particles or the top surface of theparticles which are exposed to the vapor. This could limit the amount ofcarbon nanofilaments produced on the activated carbon particle surface,because not all surfaces of the stationary activated carbon particlesand deposited precursors may be exposed to the carbonaceous vapor. Incontrast to the stationary configuration, agitating or fluidizing theactivated carbon particles and deposited nanofilament precursors willensure the carbonaceous vapor contacts more surface area of theactivated carbon particles and deposited precursors, thus yielding morecarbon nanofilaments produced on the activated carbon particlessurfaces. Reactors suitable to agitate the activated carbon particlesmay include, but are not limited to, fluidized bed reactors, rotatingbed reactors, conventional fixed bed reactors comprising agitating ormixing components, etc.

The carbonaceous vapor may comprise any carbonaceous vapor, which iseffective in providing the desired reaction product. In one embodiment,the carbonaceous vapor may comprise acetylene, benzene, xylene,ethylene, methane, ethanol, carbon monoxide, camphor, naphthalene, ormixtures thereof. The reaction conditions of temperature, time, andatmosphere may vary, and various combinations are suitable to promotethe desired reaction. In one embodiment, the temperature may vary fromabout 400° C. to about 1500° C. In exemplary embodiments, thetemperature range may comprise upper limits of less than about 1200° C.,less than about 1000° C., or less than about 800° C., and lower limitsof more than about 400° C., more than about 500° C., more than about600° C., or more than about 700° C. In another embodiment, the reactiontime is about 2 minutes to about 10 hours. In exemplary embodiments, thereaction time is from about 5 minutes to about 8 hours, from about 10minutes to about 7 hours, or from about 20 minutes to about 6 hours.

In one embodiment, the nanofilament precursors may generatenanoparticles on the surface of the activated carbon particles duringthe initial stages of the method. For example, ferric sulfate willdecompose and generate Fe nanoparticles on the surface of the activatedcarbon particles. These nanoparticles will then catalyze the formationof carbon nanofilaments as the carbonaceous vapors are carried over thecatalyst particles to build the carbon nanofilaments.

Moreover, the method may further comprise a carrier gas to deliver thecarbonaceous vapor to the surface of the carbon particles. The reactionatmosphere may comprise the carbonaceous vapor and the carrier gas thatbrings them in contact with the activated carbon particles andnanofilament precursors during the reaction. The carrier gas can beinert or reducing, and, in one embodiment, it can contain small amountsof steam. A typical and non-limiting example of such a carrier gas isnitrogen. Argon and helium are two other examples of carrier gases;however, numerous other suitable carrier gases are contemplated herein.The face velocity of the carrier gas in the furnace is from about 1cm/h.g (i.e., centimeters per hour and gram of activated carbonparticles) to about 350 cm/h.g, and in exemplary embodiments, from about2 cm/h.g to about 180 cm/h.g, from about 4 cm/h.g to about 90 cm/h.g, orfrom about 20 cm/h.g to about 40 cm/h.g.

In accordance with another embodiment of the present invention, analternative method of making filter material 28 for producing potablewater is described herein. The method comprises providing carbonizedcarbon particles. As stated above, carbonized particles are filterparticles, which have not yet undergone an activation step. Similar tothe other method described above, the method further comprisesdepositing at least partially one or more nanofilament precursors ontothe surface of the carbonized carbon particles, and agitating thecarbonized carbon particles and deposited nanofilament precursors in thepresence of carbonaceous vapor. The carbonized carbon particles and thedeposited nanofilament precursors are then heated in the presence ofcarbonaceous vapor at a temperature and time sufficient to producecarbon nanofilaments on the surface of the carbonized carbon particles.The method then includes activating the carbonized carbon particles.During activation, the carbonized particles and carbon nanofilaments areheated or chemically treated to produce the filter material, whichcomprises activated carbon particles having carbon nanofilaments on thesurface of the particles.

The carbonized carbons may be heat activated under various processingconditions well known to one skilled in the art. For example, the heatactivation may occur in an atmosphere comprising steam, CO₂, or mixturesthereof. Moreover, the activation temperatures and duration may varydepending on the filter particles used. Carbonized carbons may also bechemically activated with any suitable chemical reagent known to oneskilled in the art. For example, the carbonized carbons may be treatedwith KOH, or H₃PO₄. The activation step may be incorporated at any stageof the above-described methods. Activation may occur in one or multiplesteps, and activated carbon particles may undergo further activation.

In a further embodiment, the above-described methods may furthercomprise a cleaning step directed to cleaning the carbon nanofilamentsand substantially removing any remaining nanofilament precursors afterthe heating step. Like activation, the cleaning step may incorporateheat treatment or chemical treatment in order to clean the nanofilamentsand remove nanofilament precursors. Any cleaning procedure may beemployed. In one embodiment of chemical cleaning, an acid solution maybe used. In an exemplary embodiment, a strong acid solution, forexample, a nitric or sulfuric acid solution may be used in the cleaningstep. It is contemplated that an activation step utilized after theformation of the carbon nanofilaments, as described above, may act as acleaning step or a partial cleaning step.

In a further embodiment, the above-described methods may comprisetreating the carbonized or activated carbon particles and depositednanofilament precursors with a reducing agent prior to the heating step.During this reduction step, the particles and deposited nanofilamentprecursors are treated in the presence of reducing agents tofunctionalize the particle surface. By functionalizing the surface, thefilter particles may improve its adsorption to targeted contaminants ina water stream. Non-limiting examples of reducing agents includehydrogen, ammonia, or mixtures thereof. For example, a reducing agentcomprising ammonia may react with the particle surface to producenitrogen on the surface of the particle, wherein the nitrogen may bindor adsorb to a contaminant to be filtered.

III. Experimental Examples

The following non-limiting examples describe filter materials, andmethods of making filter materials in accordance with one or moreembodiments of the present invention.

Example 1 Formation of Activated Carbon Particles with Surface-GrownNanofilaments Using Ferrocene

100 g of the NUCHAR™ RGC 80×325 wood-based activated carbon particlesfrom MeadWestvaco Corp., of Covington, Va., are mixed with 500 mLsolution of 10% ferrocene (Fe(C₅H₅)₂) in xylene. The resulting activatedcarbon with adsorbed ferrocene is dried overnight at room temperature.The activated carbon is then loaded into the tray of the horizontal tubefurnace Lindberg/Blue M (Model # HTF55667C; SPX Corp.; Muskegon, Mich.).The diameter of the tube furnace is 15.25 cm (6 in.). The furnace isheated to 800° C. in 15 ft³/h nitrogen flow. Once the desired furnacetemperature is reached, a 10 mL/min solution of 10% ferrocene in xyleneis carried into the tube furnace by a nitrogen stream of 15 ft³/h (i.e.,face velocity of about 23 cm/h.g) for 1 h. At the end of that period,the material is allowed to cool to room temperature in a nitrogenatmosphere. The resulting activated carbon particles containsurface-grown nanofilaments.

Example 2 Formation of Activated Carbon Particles with Surface-GrownNanofilaments Using Ferric Sulfate and Ferrocene

100 g of microporous coconut activated carbon particles 80×325 fromCalgon Carbon Corp., of Pittsburgh, Pa., are mixed with 100 mL solutionof 20% ferric sulfate (Fe₂(SO₄)₃) in deionized water. The resultingactivated carbon with adsorbed ferric sulfate is dried overnight in anoven at 130° C. The activated carbon is then loaded into the tray of thehorizontal tube furnace Lindberg/Blue M (Model # HTF55667C; SPX Corp.;Muskegon, Mich.). The diameter of the tube furnace is 15.25 cm (6 in.).The furnace is heated to 800° C. in 15 ft³/h nitrogen flow. Once thedesired furnace temperature is reached, the activated carbon is held atthat temperature for about 45 min. Then, a 4 mL/min solution of 10%ferrocene in xylene is carried into the tube furnace by a nitrogenstream of 5 ft³/h (i.e., face velocity of about 8 cm/h.g) for 1 h. Atthe end of that period, the material is allowed to cool to roomtemperature in a nitrogen atmosphere. The resulting activated carbonparticles contain surface-grown nanofilaments.

It is noted that terms like “specifically,” “preferably,” “typically”,and “often” are not utilized herein to limit the scope of the claimedinvention or to imply that certain features are critical, essential, oreven important to the structure or function of the claimed invention.Rather, these terms are merely intended to highlight alternative oradditional features that may or may not be utilized in a particularembodiment of the present invention. It is also noted that terms like“substantially” and “about” are utilized herein to represent theinherent degree of uncertainty that may be attributed to anyquantitative comparison, value, measurement, or other representation.

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A filter for producing potable water comprising: a housing includinga water inlet and a water outlet; and a filter material arranged withinthe housing comprising, activated carbon particles; and a plurality ofcarbon nanofilaments disposed on the surface of the activated carbonparticles, wherein the filter is operable to provide potable water byremoving contaminants from a liquid water stream flowing from the waterinlet to the water outlet of the housing, wherein the plurality ofcarbon nanofilaments are surface-grown on the surface of the activatedcarbon particles.
 2. A filter according to claim 1 wherein the activatedcarbon particles comprise micropores, mesopores, or combinationsthereof.
 3. A filter according to claim 1 wherein the activated carbonparticles comprise wood-based activated carbon particles, coal-basedactivated carbon particles, peat-based activated carbon particles,pitch-based activated carbon particles, tar-based activated carbonparticles, or combinations thereof.
 4. A filter according to claim 1wherein the activated carbon particles comprise fibers, spheres,irregular-shaped particles, or combinations thereof.
 5. A filteraccording to claim 1 wherein the activated carbon particles have a sizeof from about 0.1 μm to about 10 mm.
 6. A filter according to claim 1wherein the carbon nanofilaments comprise single-wall nanotubes (SWNTs),double-wall nanotubes (DWNTs), multi-wall nanotubes (MWNTs),nanofilaments, nanoribbons, nanohorns, or combinations thereof.
 7. Afilter according to claim 1 wherein the filter is configured toaccommodate a flow rate of up to about 8 L/min of water.